The present invention relates to an automatic sheet feeder having a hopper and a stacker, and more particularly to an automatic sheet feeder capable of switching sheet feed mode between an automatic sheet feeding mode in which the automatic sheet feeder operates to feed a sheet automatically and a mode in which a continuous-form sheet or a manually inserted sheet is printed.
Heretofore, in a printer capable of performing printing on a continuous-form sheet, a plurality of cut sheets can also be subjected to continuous printings. In the latter case, an automatic sheet feeder having a hopper and a stacker is detachably secured to the printer. The hopper is adapted to be arranged to store cut sheets in a stacking state and to supply each one of the cut sheet to a print assembly of the printer. The stacker is adapted to store cut sheets in a stacking state after the cut sheets are printed and discharged from the print assembly.
In accommodating the printed cut sheets on the stacker with a stacking mode, a plurality of the printed cut sheets can be automatically stacked or ordered one by one from a small number of pages to the large number of pages, if a print image surface of each of the printed cut sheets faces downwardly, and subsequent printed cut sheets are continuously stacked one by one onto the non-printed surface of the precedent printed cut sheets.
In order to provide a stacker for such automatic page order printings, conventionally, the hopper is disposed rearwardly of a sheet discharge port, and the stacker is disposed in front of the sheet discharge port. Further, an upper end of the stacker is positioned frontwardly and is directed upwardly. Thus, generally V-shaped layout is provided when viewing the stacker and the hopper from a side of the printer.
However, as described above, in the V-shape arrangement of the hopper and the stacker, if the stacker is positioned at its lower position positioned adjacent the sheet discharge port of the printer, the following problems may be caused when printing to the continuous-form sheet.
That is, in case of the printing operation to the continuous-form sheet, a cutter member (having an elongated plate shape) is provided at the sheet discharge port positioned above a platen in order to cut the continuous-form sheet after printing. The continuous-form sheet passes at a rear surface of the cutter member, and a front surface of the continuous-form sheet abuts an upper edge of the cutter member when the continuous-form sheet is pulled frontwardly and is cut in transverse direction thereof.
Accordingly, the stacker obstructs a way of the continuous-form sheet which passes beside the rear surface of the cutter member and is directed upwardly. Thus, the continuous-form sheet must be pulled out frontwardly of the printer, and the cutting operation to the continuous-form sheet cannot be smoothly performed.
In order to eliminate these drawbacks, according to a conventional arrangement, the automatic sheet feeder is detached from the printer in case of printing to the continuous-form sheet, which is troublesome, and incurs difficulty since the detached automatic sheet feeder must temporarily be stored in a given location.
One typical example of an automatic sheet feeder for use in a printer is disclosed in a commonly assigned copending U.S. patent application Ser. No. 07/615,172 filed on Nov. 19, 1990 now U.S. Pat. No. 5,118,090. The disclosed automatic sheet feeder includes a stacker which can be retracted from the sheet discharge slot of a printer. When the stacker is retracted, there is defined a path for a manually inserted sheet or a continuous-form sheet.
Further, according to the sheet feeder disclosed in the copending application and used in a printer capable of performing printing to a continuous-form sheet, a plurality of cut sheets can be continuously printed by an automatic sheet feeder. The disclosed device includes a sheet feed roller for feeding cut sheets stacked in a hopper to a platen of a printer and intermediate roller pair disposed between the sheet feed roller and the platen. A drive source such as a stepper motor is disposed in the printer for driving the platen etc., and a gear transmission mechanism is provided for transmitting power to the sheet feed roller etc. from the drive source.
According to the arrangement in which the drive source of the printer is transmitted to the automatic sheet feeder, if the printing to the continuous-form sheet is carried out while the automatic sheet feeder is assembled to the printer, the sheet feed roller etc. are automatically rotated, so that the cut sheets accommodated in the hopper are fed to the print assembly. To avoid this drawback, it is necessary to shut off the power transmission to the automatic sheet feeder in case of the printing to the continuous-form sheet.
Further, the stacker which accommodates therein printed cut sheets must be moved away from the sheet discharge slot positioned above the print assembly, otherwise it becomes difficult to pull out the printed continuous-form sheet from the sheet discharge slot due to the existence of the stacker.
Furthermore, according to the related invention disclosed in the copending U. S. Patent Application, for printing to the cut sheets, the platen, the sheet feed roller and the intermediate roller pair are rotated in normal direction for nipping a leading end portion of the cut sheet between the platen and a pinch roller in contact therewith. Next, the rotations of these rollers are intermittently stopped for a short period of time, and then, platen is reversely rotated while the intermediate roller pair are normally rotated in a short period. Thus, flexed or slackened portion is provided at the leading end portion of the cut sheet between the platen and the intermediate roller pair because of the sheet feeding motion of the intermediate roller pair. By this flexed or slackened portion of the cut sheet, leading edge of the cut sheet can be oriented approximately in parallel with an axial direction of the platen, and can be obtained a generally constant contacting angle of the leading end portion of the cut sheet with respect to a contact portion between the platen and the pinch roller.
Accordingly, if the platen and the intermediate roller pair are again rotated in the normal direction, the leading end portion of the cut sheet nipped between the platen and the pinch roller is fed toward the print head with generally constant feed amount of the leading end portion. Therefore, print start position can be precisely provided on the cut sheet, and a printing line can be directed in parallel with a leading edgeline of the cut sheet.
As described above, drive force from the platen side (printer side) is transmitted to the intermediate roller pair through a gear transmission mechanism. In this case, the intermediate roller pair are rotatable in a normal direction regardless of the switching of the rotational direction of the platen. However, the present inventor has found necessity in improvement on the related invention described in the copending U.S. Patent application, now U.S. Pat. No. 5,118,090.